Glass-ceramic cooktop burner assembly having an optical sensor

Abstract

The field of view of an optical sensor used in a burner assembly of a glass-ceramic cooktop appliance is improved by providing the burner assembly with a wide angle optical element. The burner assembly includes a burner casing having a bore formed therein. The optical sensor is located in the lower end of the bore, and the wide angle optical element is located in the upper end of the bore. The wide angle optical element directs radiation from over the entire heated portion of the glass-ceramic plate onto the optical sensor. The a wide angle optical element also prevents dust from falling onto the sensor. In one preferred embodiment, the wide angle optical element is a Fresnel lens.

What is claimed is:  
     
       1. A burner assembly for a cooktop appliance, said burner assembly comprising: 
       a burner casing having a bore formed therein, said bore having an upper end and a lower end;  
       a sensor located in said lower end of said bore; and  
       a wide angle optical element located in said upper end of said bore.  
     
     
       2. The burner assembly of claim  1  wherein said wide angle optical element is a Fresnel lens. 
     
     
       3. The burner assembly of claim  2  wherein said Fresnel lens is circular and has a diameter that is equal to the diameter of said upper end of said bore. 
     
     
       4. The burner assembly of claim  2  wherein said Fresnel lens has facets formed on one side thereof. 
     
     
       5. The burner assembly of claim  1  wherein said burner casing comprises a base portion and a hub extending downwardly from said base portion, said bore being formed in said hub. 
     
     
       6. The burner assembly of claim  5  wherein said wide angle optical element is coplanar with said base portion. 
     
     
       7. The burner assembly of claim  1  wherein said bore is tapered so that said upper end is larger than said lower end. 
     
     
       8. The burner assembly of claim  1  further comprising an energy source secured to said burner casing. 
     
     
       9. The burner assembly of claim  1  wherein said sensor is an optical temperature sensor. 
     
     
       10. A burner assembly for a cooktop appliance having a glass-ceramic cooking surface, said burner assembly comprising: 
       a burner casing located under said glass-ceramic cooking surface and having a bore formed therein, said bore having an upper end and a lower end;  
       an energy source secured to said burner casing;  
       a sensor located in said lower end of said bore so as to receive radiation from said glass-ceramic cooking surface; and  
       a Fresnel lens located in said upper end of said bore.  
     
     
       11. The burner assembly of claim  10  wherein said Fresnel lens is circular and has a diameter that is equal to the diameter of said upper end of said bore. 
     
     
       12. The burner assembly of claim  10  wherein said Fresnel lens has a plurality of facets formed on one side thereof. 
     
     
       13. The burner assembly of claim  12  wherein one of said plurality of facets that corresponds to a location of said glass-ceramic cooking surface that is known to develop hot spots is larger than other ones of said plurality of facets. 
     
     
       14. The burner assembly of claim  10  wherein said burner casing comprises a base portion and a hub extending downwardly from said base portion, said bore being formed in said hub. 
     
     
       15. The burner assembly of claim  14  wherein said Fresnel lens is coplanar with said base portion. 
     
     
       16. The burner assembly of claim  10  wherein said bore is tapered so that said upper end is larger than said lower end. 
     
     
       17. The burner assembly of claim  10  wherein said sensor is an optical temperature sensor.